(a) Field of the Invention
The present invention relates to a screw driver, and more particularly to a ratchet screw driver.
(b) Description of the Prior Art
A typical ratchet screw driver is disclosed in U.S. Pat. No. 5,142,953 to Lin and comprises a post extended through a notch formed in the shaft so as to rotate the shaft and in order to rotate the pawl, and so as to change the active directions of the ratchet screw driver; in this patent, it is difficult to form the indent in the head in order to receive the pawl, furthermore, the pawl can not be easily engaged in the indent such that the operators may waste much time to locate and to assemble the pawl, the pin for positioning the pawl can not be easily engaged in place, in addition, the notch should be formed in the shaft such that the post may extend and may be engaged with the rod, the notch greatly reduces the strength of the shaft and greatly weaken the shaft such that the working life of the screw driver is greatly decreased, and such that this kind of screw driver can not be commercialized.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional ratchet screw drivers.